Wound capacitor

ABSTRACT

There is disclosed a wound capacitor which is designed to open an external circuit upon capacitor failure. This is accomplished by dividing the foil at each end of the capacitor into two regions. A lead is then connected to each region so that the completed capacitor has a total of four leads. The two leads at each end of the capacitor become a part of the external circuit. A capacitor failure thereby causes an open in the external circuit.

BACKGROUND OF THE INVENTION

Certain type of circuits require the presence of a capacitor forpurposes of safety. One such circuit is the circuit energizing a colortelevision tube. A capacitor is required across this circuit in order tosupress harmful radiation from the tube. In the absence of such acapacitor, the tube may emit radiation which can cause severe harm toliving things. In the past, if a capacitor in such a circuit exhibitedcertain failure modes, the main circuit would act as if there were nocapacitor at all and it would then emit radiation. These failure modeswere either a complete open, an intermittent open or physical removal ofthe capacitor from the circuit. By "intermittent" is meant a situationin which a lead is broken away from the capacitor but, under certaincircumstances such as temperature variations or vibration, will makecontact.

Accordingly, it is a primary object of the present invention to providea capacitor which, upon failure, will disable the main circuit. Otherobjects are to provide such a capacitor which will so disable a circuitupon the occurrence of a break between the capacitor lead and winding;upon an intermittent break; upon occurrence of a broken or cut lead;upon complete removal of the capacitor from the circuit; and uponremoval of the capacitor winding leaving the leads and end fill stillintact.

The manner in which the foregoing objects are achieved will be apparentfrom the following description and appended claims.

SUMMARY OF THE INVENTION

An improvement in a wound capacitor of the type having first and secondconductive plates separated by a dielectric, the first plate beingexposed at one end and the second plate being exposed at the other endof the capacitor. The improvement comprises provision of at least twoleads connected to the plate exposed at each end of the capacitor. Theleads are secured to the plate in spaced relationship to each other.

BRIEF DESCRIPTION OF THE DRAWING

With particular reference to the drawing:

FIG. 1 illustrates a wound capacitor partially unrolled to illustrateits construction;

FIG. 2 illustrates one end of a capacitor winding in accordance withthis invention;

FIG. 3 illustrates a completed capacitor in accordance with theinvention, partially broken away to illustrate its internalconstruction;

FIG. 4 illustrates a failure mode of a capacitor in accordance with theinvention; and

FIG. 5 illustrates diagrammatically the manner in which a capacitor inaccordance with this invention is connected to a load.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There is illustrated in FIG. 1 a partially unrolled capacitor comprisinga dielectric film or sheet 10 separating foil 12 forming a firstcapacitor plate and a foil 14 forming a second capacitor plate. Thefoils are staggered so that, after being rolled, the foil 12 extendsfrom the left end of the capacitor as viewed in FIG. 1, while the foil14 extends from the right end of the capacitor. A second dielectric 16also separates the foils and encircles the completed capacitor to forman outer wrapping.

In a conventional capacitor, a single lead would be soldered to the foilat each end of the rolled capacitor. In the case of aluminum foil, atechnique called "swedging" is used. Aluminum solder is applied to thefoils under heat and pressure, thereby permitting a lead to be attachedusing additional solder. Various welding processes are also in use forattaching the leads to aluminum foil. In accordance with the presentinvention, however, two leads are connected to each end of the capacitorin spaced relation to one another. Thus, as seen in FIG. 2, the leads 18and 20 are soldered to the foil 12. A corresponding pair of leads 22, 24are similarly attached to the opposite end of the capacitor. Further, inthe manufacture of a capacitor in accordance with the invention, aportion of the foil intermediate the leads 18, 20 is removed to form aslot 26. The slot 26 extends to a depth even with the edge of thedielectric 10, 16. Thereafter, an insulating tape 28 is wrappedlengthwise around the capacitor and through the slot 26 in one end andthe corresponding slot in the other. Thereafter, the capacitor isencapsulated. This may be done as shown in FIG. 3, for example, by meansof a porcelain tube 30 and a suitable end fill 32, such as an epoxy, asshown in FIG. 3.

The manner in which the capacitor of this invention is employed toprotect a circuit is illustrated in FIG. 5, which illustrates a powersource such as a transformer winding 34 and a load 36 to be protectedwhich may include, as explained above, a television tube. It isimportant to note that when the capacitor of this invention is connectedinto a circuit as disclosed in FIG. 5, the leads of the capacitor becomea part of the load circuit itself. It will thus be apparent that if, forexample, one lead 20 were to pull away from the capacitor as shown inFIG. 4, this would constitute an open circuit in the load itself andthereby prevent it from operating. A similar result would occur from anintermittent open, a broken lead, complete removal of the capacitor fromthe circuit, or complete removal of the capacitor winding leaving theleads and end fills still intact. The presence of the slot 26 and tape28, prevents any "bridging" foil from remaining between the leads 18, 20in the event they are singly or simultaneously detached from thecapacitor.

It is believed that the many advantages of this invention will now beapparent to those skilled in the art. It will also be apparent that anumber of variations and modifications may be made in this inventionwithout departing from its spirit and scope. For example, various typesof capacitor windings might be employed such as, for example, ametallized construction wherein each plate is a deposit of metal applieddirectly to the dielectric. Accordingly, the foregoing descriptionshould be construed as illustrative only, rather than limiting. Thisinvention is limited only by the scope of the following claims.

I claim:
 1. In a wound capacitor of the type having first and secondconductive plates separated by a dielectric, the first plate beingexposed at one end, and the second plate being exposed at the other end,of the capacitor, the improvement which comprises: at least two leadsconnected to the plate exposed at each end of said capacitor, said leadsbeing secured to the plate in spaced relationship to each other, theexposed plate at each end defining a slot between said leads.
 2. Thecapacitor of claim 1 wherein each of said slots includes an insulatingtape extending therethrough.
 3. The capacitor of claim 1 wherein saidslot is substantially filled with an insulating material.
 4. In a woundcapacitor of the type having first and second conductive platesseparated by a dielectric, the first plate being exposed at one end, andthe second plate being exposed at the other end, of the capacitor, saiddielectric encircling the fully wound capacitor with its edges displacedinwardly from the exposed edges of said plates, the improvement whichcomprises: at least two leads connected to the plate exposed at each endof said capacitor the exposed plate at each end defining a slot betweensaid leads having a depth substantially equal to the exposed portion ofsaid plates.
 5. The capacitor of claim 4 wherein each of said slotsincludes an insulating tape extending therethrough.
 6. The capacitor ofclaim 4 wherein said slot is substantially filled with an insulatingmaterial.
 7. In a wound capacitor of the type including first and secondmetallic foil strips separated by first and second dielectric strips,one of said dielectric strips encircling the fully wound capacitor buthaving said first foil strip exposed at one end thereof and the secondfoil strip exposed at the other end, the improvement which comprises:two leads connected to the foil exposed at each end of said capacitor inspaced relationship to each other; a slot between said leads defined bythe foil at each end of said capacitor, and having a depth substantiallyequal to the exposed projection of foil; and insulating means enclosingsaid capacitor and substantially filling each of said slots but leavingthe leads exposed.
 8. The capacitor of claim 7 wherein each of saidslots includes an insulating tape extending therethrough.
 9. In a woundcapacitor of the type having first and second conductive platesseparated by a dielectric, the first plate being exposed at one end, andthe second plate being exposed at the other end, of the capacitor, theimprovement which comprises: at least two leads connected to the plateexposed at an end of said capacitor, said leads being secured to theplate in spaced relationship to each other, said exposed plate defininga slot between said leads. .Iadd.10. In a wound capacitor of the typehaving a body including first and second conductive plates separated bya dielectric, the first plate being exposed at one end, and the secondplate being exposed at the other end, of the capacitor, the improvementwhich comprises: at least two leads connected to the plate exposed at anend of said capacitor body, said leads being secured to the plate inspaced relationship to each insulating means encapsulating saidcapacitor body with said leads extending therethrough other separationand means extending sustantially diametrically across the end of saidcapacitor body intermediate said leads and intermediate said plate andinsulating means for preventing conductive material bridging said leadsupon detachment of a lead from said capacitor. .Iaddend..Iadd.11. In awound capacitor of the type having first and second conductive platesseparated by a dielectric, the first plate being exposed at one end, andthe second plate being exposed at the other end, of the capacitor, theimprovement which comprises: at least two leads connected to the plateexposed at each end of said capacitor, said leads being secured to theplate in spaced relationship to each other, and means including aninsulated tape for preventing conductive plate material bridging saidleads upon detachment of a lead from said capacitor. .Iaddend.